Blackhawk SJ-2 Rebuild

[paulsomlo]

I've begun the process of rebuilding a Blackhawk SJ-2, 1.5 ton floor jack. I purchased one at auction, sight unseen, over a month ago - big mistake. Bent frame, broken casters, flat spot where tank/nut had been dragged, scored cylinder, etc.. Amazing what doesn't show in a picture. Two weeks later, another one shows up on CL, needs rebuild, $20. Having gained confidence tearing into the 1st one, I bought this second one sight unseen as well, it being 60 miles away, having it delivered to a friend's house nearby the seller, for convenience.

The 2nd one is in much better shape, and worth rebuilding. After removing the hydraulic unit, I mounted it in a shop press and used a pipe wrench on the tank nut. But, to avoid chewing up the nut, I used two 1/4" dowel pins, 3/4" long, and placed them diametrically opposite each other in the "scallops" on the nut. I used two small pieces of bar magnet to keep the dowel pins in place, while I positioned the pipe wrench. The dowels allow the wrench to be slid inboard, towards the nut/tank interface, which helps keep the wrench from slipping off the end. I used a 2 foot pipe wrench, with the jack handle lashed to it using hose clamps, for about 5 feet of extension.

As expected, the ram cup had disintegrated into a zillion little pieces that came pouring out when I removed the tank. Breaking down the hydraulic unit, everything was as expected until I removed the overload plug. Unlike the 1st one that I tore into, the 2nd one has what appears to be a lead plug where the overload adjust should be. Or is the overload adjust under the lead plug? I wouldn't mess with the overload, but given the state of the former ram cup, I'd like to give the innards a good flush. Anybody have any ideas?

Paul

 

[EDGAR]

Maybe there was a problem with the overload, like it was leaking, for example, or a part was lost, and the previous owner decide to plug it with lead. Probably all the parts were removed to make it easy to fill the hole but the small hole at the bottom may have been blocked to prevent the lead from entering the oil galleries. The jack will work without it but it will not bypass if the load the seal, or the chassis itself, can withstand is exceeded which should be more than the rating for the jack. Not really necessary since you are not probably going to lift 3000 lbs at once. Still the parts themselves should be able to lift at least 4000 lbs. And if the parts are missing, then you have the problem of finding the parts plus you do not know the condition of the seat; it could be damaged and difficult to redo.

You certainly want to flush the pump to remove every tiny bit of broken seal that may otherwise in the future jam a valve ball and this may required removing all the plugs. You may remove it to flush the pump and later plug it again with lead or epoxy but do not forget to block the small hole at the bottom so nothing gets into the oil galleries.

 

[paulsomlo]

Well, turns out the lead was just covering the overload adjust. I did notice that the piece which interposes between the spring and the ball was missing, what the parts breakdown refers to as the "ball guide". I've got one from the 1st SJ-2, although the stem on it was broken off. It doesn't look like it will be too hard to duplicate on the lathe.

I've included a picture of the ram, showing the leather wiper, washer, and nut. I'm assuming this uses a piston cup, rather than the more modern u cup? If so, would it make sense to turn an adapter that threads onto the ram end, with a groove to retain a u cup? From the wiper to the end of the threaded portion is 0.55", without the wiper, about 0.65", and the threaded portion is 1/2" diameter. The brass piece on the end of the ram measures 1.536" OD, and the cylinder ID is 1.546". I'm curious - is the cylinder ID made to fit a standard piston cup, or was it peculiar to Blackhawk?

By the way, what's a good solvent to flush out the hydraulic block? I don't have a parts washer, so I'll be doing it in a bucket. Would mineral spirits work? I've also got Simple Green. The original packing for the release valve is still intact and tightens down nicely on the stem - it might be good if the solvent didn't attack it. Or maybe it's such a cheap part, that it doesn't matter.

Paul